\(\diamond \)  SPAM Researchers have adopted the most common feature extractors. One of them is proposed in a research study presented by Pevny [1]} for Subtractive Pixel Adjacency Matrix (SPAM) feature extraction from the spatial domain of the digital images. SPAM has two clusters of features: one group derived from markov-horizontal and vertical and another extracted from markov-major and minor diagonal features. Merging these two groups brings the total number of SPAM features to 686.
